1. Field of the Invention
The present invention relates to an optical structure measuring apparatus and an optical probe thereof, and more particularly to an optical structure measuring apparatus and an optical probe thereof, that are featured in a radial scanning method in which measuring light beams are radially scanned across an object to be measured by the measuring light beams.
2. Description of the Related Art
Conventionally, when an optical tomographic image of a living tissue is obtained, an optical tomographic image obtaining apparatus utilizing the OCT (Optical Coherence Tomography) measurement may be used. The optical tomographic image obtaining apparatus divides a low coherent light beam emitted from a light source into a measuring light beam and a reference light beam. Thereafter, the optical tomographic image obtaining apparatus multiplexes, with the reference light beam, a light beam reflected or back-scattered by a measuring object at the time of irradiating the measuring light beam onto the measuring object, and obtains an optical tomographic image on the basis of the intensity of the interference light beam of the reflected light beam and the reference light beam (Japanese Patent Application Laid-Open No. 2008-128708).
The above-described OCT measurement is roughly divided into two kinds: the TD-OCT (Time domain OCT) measurement and the FD-OCT (Fourier Domain OCT) measurement.
The TD-OCT measurement is a method in which a reflected light beam intensity distribution corresponding to a depth direction position (hereinafter referred to as depth position) of a measuring object is obtained by measuring the intensity of the interference light beam while changing the optical path length of the reference light beam.
On the other hand, the FD-OCT measurement is a method in which the intensity of the interference light beam is measured for each spectral component of the light beam without changing the optical path of the reference light beam and the signal light beam, and in which the frequency analysis (as represented by the Fourier transform) of the spectral interference intensity signals obtained by the measurement is performed by a computer so that a reflected light beam intensity distribution corresponding to a depth position is obtained. In recent years, the FD-OCT measurement has been attracting attention as a method which does not need the mechanical scanning necessary for the TD-OCT measurement, and which can perform the measurement at high speed.
As shown in FIG. 16, an OCT probe 800 used for the conventional OCT measurement acquires a return light beam L3 in such a manner that an optical fiber FB1 and a torque transmitting coil 824, which are provided on the rotation side, are rotated by an optical rotary joint (not shown) in the arrow R direction in FIG. 16, and that a measuring light beam L1 emitted from an optical lens 828 is thereby irradiated onto a measuring object S while the radial scanning is performed along the arrow R direction.
Thereby, over the entire circumference in the circumferential direction of a sheath 820 of the OCT probe 800, it is possible to accurately capture desired portions of the measuring object S and possible to obtain the return light beam L3 reflected by the measuring object S.
Further, when a plurality of pieces of optical structure information are obtained in order to generate an optical three-dimensional structure image, the optical lens 828 is moved by an axial movement driving section to an end of the region in which the optical lens 828 can be moved in the arrow S1 direction. Then, the optical lens 828 is moved in the S2 direction by each predetermined amount while optical structure information of the tomogram is acquired, or is moved to the end of the movable region while the acquisition of the optical structure information and the movement by the predetermined amount in the S2 direction are alternately repeated.
In this way, the plurality of pieces of optical structure information of the desired range of the measuring object S are obtained, so that an optical three-dimensional structure image can be obtained on the basis of the acquired plurality of pieces of optical structure information.
That is, while the optical structure information in the depth direction (first direction) of the measuring object S is acquired on the basis of the interference signal, the radial scanning of the measuring object S is performed in the arrow R direction (circumferential direction of the sheath 820) in FIG. 16. Thereby, it is possible to obtain the optical structure information on the scanning surface which is formed by the depth direction (first direction) of the measuring object S and the direction (second direction) substantially orthogonal to the depth direction. Further, a plurality of pieces of optical structure information used for generating an optical three-dimensional structure image can be obtained by moving the scanning surface along the direction (third direction) substantially orthogonal to the scanning surface.
On the other hand, an OCT probe is disclosed, for example, in Japanese National Publication of International Patent Application No. 2004-502957, in which a plurality of light beams emitted from a plurality of optical fibers are simultaneously scanned along the optical axis by arranging the plurality of optical fibers and an optical path converging device so as to allow the focal points of the light beams to be formed at continuous positions, and in which the continuous focal points are scanned by a mirror in the lateral direction with respect to the optical axis so that the continuous focal points can be scanned over a two-dimensional region.
Further, an OCT probe is disclosed, for example, in Japanese Patent Application Laid-Open No. 2001-51225, in which a light beam emitted from an optical fiber is irradiated onto a measuring object by using a polygon mirror having a plurality of reflecting surfaces with mutually different reflection angles, and in which a predetermined two-dimensional region can be obtained at high speed by rotating the polygon mirror.